This project is designed to understand the role of hormones and growth factors in normal mammary gland development and differentiation. We wish to understand how milk-protein production is controlled by various hormones. Studies include: 1) examination of the role of thyroid hormones, adrenal steroids and Vitamin D in synthesis and secretion of milk proteins in organ culture, 2) examination of the role of epidermal growth factor and mammary gland-derived growth factors in lobulo-alveolar development of the immature mouse mammary gland.